1. Field of the Invention
The present invention relates to a vibration wave driving device such as a vibration wave motor, etc., an image forming device and a device using the vibration wave motor as a driving source.
2. Related Background Art
A controller utilizing a motor as a driving source generally requires that a driving member be repeatedly operated by the motor while a certain precise level is held.
In particular, in an image forming device in an electrophotographic system, the use of a motor of a higher rotational accuracy is required as a motor for driving a photosensitive drum used as an image bearing member to form a high accuracy image, or as a motor for driving a transfer member for driving a transfer member conveying belt, e.g., an endless belt which conveys a transfer member such as transfer paper, etc., toward a transfer position of the photosensitive drum. To achieve this object, it has been proposed to use a vibration wave device such as a vibration wave motor as a motor for driving the photosensitive drum, or a motor for driving the transfer member.
For example, as is publicly known in Japanese Patent Application Laid-Open No. 58-14682, etc., the vibration wave motor as a vibration wave device is a motor utilizing vibration. For example, the vibration wave motor is constructed of a vibration member formed by joining an electro-mechanical energy conversion element such as a piezoelectric element to an elastic member made of a metal, etc., and a contact member brought into pressure contact with the elastic member. A driving vibration (travelling wave vibration) is generated on a contact face of the elastic member in contact with the contact member by applying a periodic signal to the piezoelectric element. The vibration member and the contact member are relatively moved by frictional vibration energy of this driving vibration.
Here, for example, when the vibration member is set to a stator, the contact member is set to a rotor, and the rotor is attached to a rotating shaft arranged at a center of rotation of the rotor, the rotating shaft is rotated integrally with this rotor.
As described in detail in Japanese Patent Application Laid-Open Nos. 63-1379, 60-176470, 59-204477, etc., with respect to driving control of the vibration wave motor, a driving frequency, a driving voltage and a pulse width of the driving voltage signal used as control amounts are adjusted at any time in accordance with the difference between a speed signal from a speed detecting means, such as an encoder signal for detecting the rotation of the vibration wave motor and a preset target speed. Thus, stable rotating performance at constant speed is realized by so-called speed feedback loop control.
An object of the invention is to provide a vibration wave driving device and an image forming device capable of improving the driving characteristics of a vibration wave device such as a vibration wave motor.
In one aspect of the application in the above object, a high speed mode for driving the vibration wave motor at a high speed in comparison with a normal driving speed is set, and a use or operating state of the device, etc., is determined and rotating characteristics of the vibration wave motor are improved by driving the vibration wave motor in the high speed mode in accordance with the results of this determination.
In one aspect of the application, a rotational speed of the vibration wave motor in the high speed mode is set to be higher than a driving speed at the time of a predetermined operation performed by driving the vibration wave motor.
In one aspect of the application, a high speed mode, for driving the vibration wave motor at a speed higher than a driving speed during performing of, specific processing, is set in a device for performing plural processings by driving the vibration wave motor, it is determined whether or not it conforms to a predetermined condition during execution of this high speed mode, and in which execution of the high speed mode is inhibited while performing the specific processing and is allowed in accordance with a use state of the device, etc.
In one aspect of the application, a driving mode for improving stable rotating characteristics of the vibration wave motor is provided and is selectively executed by discriminating a situation of the device, etc.
Other objects of the present invention will become more apparent from embodiments explained below.